8 Channel Capacitive Touch Sensor with 2 LED Drivers
Datasheet
used for touch detection. So long as the bit is set for a particular channel, the delta count value is reset
to 00h and thus no touch is detected.
These bits are not sticky and will be cleared automatically if the analog block does not report a noise
error.
APPLICATION NOTE: If the MTP detection circuitry is enabled, these bits count as sensor inputs above the MTP
threshold (see Section 4.5.4, "Multiple Touch Pattern Detection") even if the corresponding
delta count is not. If the corresponding delta count also exceeds the MTP threshold, it is not
counted twice.
APPLICATION NOTE: Regardless of the state of the Noise Status bits, if low frequency noise is detected on a
sensor input, that sample will be discarded unless the DIS_ANA_NOISE bit is set. As well,
if RF noise is detected on a sensor input, that sample will be discarded unless the
DIS_RF_NOISE bit is set.
5.4
Sensor Input Delta Count Registers
Table 5.6 Sensor Input Delta Count Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Sensor Input 1
Delta Count
10h
11h
12h
13h
14h
15h
16h
17h
R
Sign
64
32
16
8
4
2
1
00h
Sensor Input 2
Delta Count
R
R
R
R
R
R
R
Sign
Sign
Sign
Sign
Sign
Sign
Sign
64
64
64
64
64
64
64
32
32
32
32
32
32
32
16
16
16
16
16
16
16
8
8
8
8
8
8
8
4
4
4
4
4
4
4
2
2
2
2
2
2
2
1
1
1
1
1
1
1
00h
00h
00h
00h
00h
00h
00h
Sensor Input 3
Delta Count
Sensor Input 4
Delta Count
Sensor Input 5
Delta Count
Sensor Input 6
Delta Count
Sensor Input 7
Delta Count
Sensor Input 8
Delta Count
The Sensor Input Delta Count registers store the delta count that is compared against the threshold
used to determine if a touch has been detected. The count value represents a change in input due to
the capacitance associated with a touch on one of the sensor inputs and is referenced to a calibrated
base “Not Touched” count value. The delta is an instantaneous change and is updated once per sensor
input per sensing cycle (see Section 4.5.1, "Sensing Cycle").
The value presented is a standard 2’s complement number. In addition, the value is capped at a value
of 7Fh. A reading of 7Fh indicates that the sensitivity settings are too high and should be adjusted
accordingly (see Section 5.5).
The value is also capped at a negative value of 80h for negative delta counts which may result upon
a release.
Revision 1.32 (01-05-12)
SMSC CAP1128
DATA4S4HEET
SMSC [ SMSC CORPORATION ]
